RESUMO
We describe two novel α2 gene mutations that result in an altered amino acid sequence. In case 1, the α2 stop codon was mutated from TAA > TTA (HBA2: c.428A > T), resulting in an α2 protein chain extension of 31 amino acids. The new hemoglobin (Hb) variant was named Hb Kinshasa for the place of origin of the patient. This patient was also a carrier of Hb S (HBB: c.20A > T), which was expressed at reduced levels, but had an otherwise normal blood count. For cases 2 and 3, an α2 frameshift mutation caused a premature α2 protein chain termination at position 133 (HBA2: c.342-345insCC). The phenotype of this mutation seems to be rather severe as judged by the pronounced microcytosis and hypochromia observed in case 2. In addition, the father of this patient (case 3) also carried a ß(0)-thalassemia (ß(0)-thal) mutation (HBB: c.118C > T).
Assuntos
Substituição de Aminoácidos , Hemoglobina A2/genética , Mutação , Fenótipo , alfa-Globinas/genética , Talassemia alfa/diagnóstico , Talassemia alfa/genética , Adulto , Anemia Falciforme/diagnóstico , Anemia Falciforme/genética , Pré-Escolar , Análise Mutacional de DNA , Índices de Eritrócitos , Feminino , Genótipo , Hemoglobina Falciforme/genética , Heterozigoto , Humanos , MasculinoRESUMO
In two unrelated families, several newborns developed cyanosis within the first days of life. For all of them, consecutive arterial blood gas analyses showed a right shift of the saturation curve, suggesting the presence of a hemoglobin (Hb) variant. A new (G)γ-globin variant was detected, namely (G)γ105(G7)Leu â His; HBG2: c.317T > A, that we named Hb F-Brugine/Feldkirch after the place of origin of the two families. This T to A conversion results in a leucine to histidine amino acid change at codon 105 of the (G)γ-globin gene and caused a Hb variant with lowered oxygen affinity. The γ to ß switch proceeded normally.
Assuntos
Hemoglobina Fetal/genética , Hemoglobinas Anormais/genética , Mutação de Sentido Incorreto , Oxigênio/metabolismo , gama-Globinas/genética , Sequência de Bases , Ligação Competitiva , Cromatografia Líquida de Alta Pressão , Cianose/genética , Cianose/metabolismo , Análise Mutacional de DNA , Feminino , Hemoglobina Fetal/metabolismo , Hemoglobinas Anormais/metabolismo , Histidina/genética , Humanos , Recém-Nascido , Leucina/genética , Masculino , Ligação Proteica , gama-Globinas/metabolismoRESUMO
A baby girl, born at term, presented with severe cyanosis and received oxygen supplementation. Consecutive arterial blood gas analysis showed a pronounced right shift of the saturation curve, suggesting the presence of a hemoglobin (Hb) variant. A new (G)γ-globin variant was detected, namely HBG2:c.308G, which we have named Hb F-Sarajevo, the city from where the baby's parents originate. This A to C transversion exists in cis to the common (A)γ(T) and the resulting mutant Hb molecule exhibits very low oxygen affinity and cooperativity. Its analogue in the ß-globin gene is Hb Kansas [ß102(G4)AsnâThr, AAC>ACC].
Assuntos
Cianose/genética , Hemoglobina Fetal/genética , Oxigênio/metabolismo , Mutação Puntual , gama-Globinas/genética , Sequência de Bases , Cianose/diagnóstico , Cianose/metabolismo , Análise Mutacional de DNA , Feminino , Hemoglobinas Anormais/genética , Humanos , Recém-Nascido , Dados de Sequência Molecular , Homologia de Sequência de AminoácidosRESUMO
We report three cases with very heterogeneous Hb A(2) levels caused by known chromosomal rearrangements in the ß-globin locus. These rearrangements had their breakpoints at the same region in the δ gene, leading either to the Senegalese δ(0)ß(+)-thalassemia (δ(0)ß(+)-thal) deletion or to an insertion of a δ gene, known as Anti-Lepore. One patient showed, apart from drastically increased Hb A(2) values of 17.0%, inconspicuous hematological values. He had an Anti-Lepore mutation with three copies of the δ gene, thus explaining the high Hb A(2) level. Two other patients had Hb A(2) levels in the lower borderline range and increased Hb F levels. Molecular analysis showed the Senegalese δ(0)ß(+)-thal deletion. One of them presented with an additional mild ß-thal mutation leading to ß-thal intermedia. These cases illustrate that different gene rearrangements with the same breakpoints in the δ gene can lead to different levels of Hb A(2) depending on the remaining number of δ genes.
Assuntos
Dosagem de Genes , Rearranjo Gênico/genética , Talassemia beta/genética , Globinas delta/genética , Adulto , DNA/química , DNA/genética , Quebras de DNA , Feminino , Hemoglobina Fetal/genética , Genótipo , Hemoglobina A2/genética , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Índice de Gravidade de DoençaRESUMO
We report the characterization of five novel delta-globin gene mutations detected during routine screening for thalassemia. Three missense mutations were identified, resulting in the following delta chain hemoglobin (Hb) variants: Hb A(2)-Acacias [delta4 (ACT>AGT), Thr-->Ser, HBD c.14C>G], Hb A(2)-Toronto [delta74 (GGC>GAC), Gly-->Asp, HBD c.224G>A], and Hb A(2)-Calgary [delta99 (GAT>GGT), Asp-->Gly, HBD c.299A>G]. Two other mutations most likely result in delta(0)-thalassemia (delta(0)-thal). One mutation altered the translation initiation codon from ATG to ATA (HBD c.3G>A), and another changed the canonical splice donor sequence of IVS-II from GT to AT (HBD C.315+1G>A).
Assuntos
Mutação , Talassemia beta/genética , Globinas delta/genética , Adulto , Alelos , Sequência de Aminoácidos , Sequência de Bases , Códon de Iniciação/genética , Análise Mutacional de DNA , Feminino , Testes Genéticos , Humanos , Masculino , Pessoa de Meia-Idade , Sítios de Splice de RNA/genética , Talassemia beta/diagnósticoRESUMO
We report the identification of two different mutations involving the first nucleotide of intron 1 of the alpha2-globin gene: IVS-I-1 G-->A and G-->T. The available data indicated that both mutations reduce the efficiency of proper mRNA splicing, resulting in alpha(+)-thalassemia (alpha(+)-thal).
Assuntos
Mutação Puntual , Splicing de RNA/genética , alfa-Globinas/genética , Talassemia alfa/genética , Idoso , Canadá , Feminino , Humanos , Íntrons , Masculino , Pessoa de Meia-Idade , SicíliaRESUMO
We report the identification of three, new beta-thalassemia (beta-thal) mutations with varying degrees of severity. The most severe mutation, a frameshift mutation in exon 3 of the beta-globin gene [codon 120 (-A)], was associated with a dominant beta-thal phenotype. A second frameshift mutation, codon 50 (-T), resulted in a phenotype of typical high Hb A(2) beta-thal trait. The mildest mutation was IVS-II-2 (T > C), which changes the splice donor sequence of IVS-II from GT to GC. This transition mutation resulted in a slight reduction in beta-globin gene expression and could be considered a mild beta(+)-thal allele.
Assuntos
Mutação , Globinas beta/genética , Talassemia beta/genética , Adulto , Sequência de Bases , Análise Mutacional de DNA , Feminino , Mutação da Fase de Leitura , Humanos , Dados de Sequência Molecular , Sítios de Splice de RNA/genética , Índice de Gravidade de Doença , Talassemia beta/patologiaRESUMO
We report a family in which two siblings are compound heterozygotes for Hb S [beta6(A3)GluVal] and a rare beta-globin mutation [IVS-I (-2) (A>C)]. Both patients had significant levels of Hb A, indicating that the IVS-I (-2) mutation is a relatively mild beta(+)-thalassemia (beta(+)-thal) allele. This mutation, in compound heterozygosity with Hb S, does not necessarily lead to a mild clinical course.
Assuntos
Alelos , Hemoglobina Falciforme/genética , Heterozigoto , Mutação Puntual , Sítios de Splice de RNA/genética , Talassemia beta/genética , Adulto , Feminino , Humanos , Masculino , IrmãosRESUMO
We describe a Hb S/beta-thalassemia (beta-thal) mutation involving an AT transition at codon 132 of the beta-globin gene. The mutation, in the heterozygous state, unlike several other mutations in exon 3, shows no signs of dominant thalassemia but those of a typical beta(0) carrier. Compound heterozygosity with Hb S [beta6(A3)GluVal, GAGGTG] showed a severe clinical picture.
Assuntos
Códon/genética , Éxons/genética , Hemoglobina Falciforme/genética , Heterozigoto , Mutação/genética , Talassemia beta/genética , África Ocidental , Família , Feminino , Humanos , MasculinoRESUMO
We describe a patient originating from Ghana who had combined heterozygous alpha (4.2)thalassemia, alpha alpha alpha anti3.7 triplication, the common delta globin variant HbA2' and a new 65 bp duplication/insertion in exon II of the b globin gene causing beta (0)-thalassemia.
Assuntos
Duplicação Gênica , Globinas/genética , Mutagênese Insercional , Proteínas Mutantes/genética , Talassemia alfa/genética , Talassemia beta/genética , Adulto , Sequência de Aminoácidos , Códon/genética , Códon de Terminação , Éxons/genética , Genótipo , Gana/etnologia , Globinas/química , Hemoglobinas/análise , Hemoglobinas/genética , Humanos , Masculino , Dados de Sequência Molecular , Proteínas Mutantes/química , Talassemia alfa/sangue , Talassemia beta/sangueRESUMO
A new beta(0) thalassemia allele caused by a TGAT insert in codon 116 of exon III was detected in a patient compound heterozygous for beta(0) thalassemia / Hb D Los Angeles and his father. The mutation unexpectedly causes a classical thalassemic phenotype. The compound heterozygosity leads to mild microcytic anemia and no further clinical signs.
Assuntos
Códon sem Sentido , Mutação da Fase de Leitura , Globinas/genética , Mutagênese Insercional , Talassemia beta/genética , Pré-Escolar , Códon/genética , Análise Mutacional de DNA , Humanos , Masculino , Fenótipo , Análise de Sequência de DNARESUMO
BACKGROUND: More than 900 hemoglobin (Hb) variants are currently known. Common techniques used in Hb analysis are electrophoretic and chromatographic assays. In our laboratory, we routinely apply chromatographic methods. To ascertain whether Hb variants are missed with our procedures, we additionally analyzed all samples with mass spectrometry (MS). METHODS: Database evaluation was performed using all entries made in the Hb variant database HbVar, and possible Hb variants were calculated based on DNA variations. During a 5-year period, we analyzed 2105 lysates with cation-exchange HPLC (PolyCAT A column) and reversed-phase HPLC and additionally with electrospray ionization or MALDI-TOF MS. Globin chains were identified by their molecular masses. RESULTS: Database evaluation revealed that 43.2% of all possible Hbalpha- and beta-chain variants were found to date (considering only single-point mutations). Currently, 68.2% of the possible charge difference variants and only 28.7% of the neutral variants are found. Among 2105 Hb samples we identified 4 samples with Hb variants that were detected only with the MS method; 2 were new Hb variants (Hb Zurich-Hottingen and Hb Zurich-Langstrasse). With cation-exchange HPLC, 1 sample was found to be a beta-thalassemia and was identified by MS to be a beta-variant (Hb Malay). More common variants, such as Hb C, Hb D, and Hb E, and thalassemias could not be detected with the MS method. CONCLUSIONS: Application of MS improves the sensitivity of Hb analysis. The combination of MS with electrophoretic and chromatographic methods is optimal for the detection of Hb variants.
Assuntos
Hemoglobinas/química , Hemoglobinas/genética , Cromatografia Líquida de Alta Pressão/métodos , Bases de Dados Factuais , Feminino , Variação Genética , Humanos , Interações Hidrofóbicas e Hidrofílicas , Masculino , Sensibilidade e Especificidade , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
A new electrophoretically and clinically silent beta-globin variant has been detected by DNA analysis. The mutation was demonstrated at the protein level by reversed phase high performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS).
Assuntos
Inativação Gênica , Variação Genética , Globinas/genética , Hemoglobinas Anormais/genética , Mutação Puntual , Espectrometria de Massas por Ionização por Electrospray/métodos , Adulto , Substituição de Aminoácidos , Pré-Escolar , Cromatografia Líquida de Alta Pressão/métodos , Códon sem Sentido , Feminino , Hemoglobinas Anormais/análise , Heterozigoto , Humanos , Focalização Isoelétrica , Masculino , Portugal/epidemiologia , IrmãosRESUMO
Two new delta-globin gene mutations have been detected: one leads to a fairly stable Hb A2 variant differing electrophoretically only minimally from normal Hb A2, and the second causes a delta(+)-thalassemia (thal) phenotype.
Assuntos
Variação Genética/genética , Globinas/genética , Hemoglobina A/genética , Mutação Puntual/genética , TATA Box/genética , Talassemia beta/genética , Adulto , Pré-Escolar , Cromatografia por Troca Iônica/métodos , Análise Mutacional de DNA/métodos , Feminino , Triagem de Portadores Genéticos , Globinas/análise , Hemoglobinas Anormais/genética , Humanos , Iraque , ItáliaRESUMO
A new alpha-globin mutation causing persistent mild hypochromic microcytosis and erythrocytosis is described. Hb Zurich Albisrieden [alpha59(E8)Gly-->Arg (alpha2)] is not detected at the protein level and leads to alpha(+)-thalassemia (thal).
Assuntos
Substituição de Aminoácidos/genética , Globinas/genética , Hemoglobinas Anormais/genética , Mutação Puntual/genética , Talassemia alfa/genética , Adulto , Humanos , Masculino , Policitemia/complicações , Policitemia/genética , Desnaturação Proteica/genética , Talassemia alfa/complicaçõesRESUMO
A novel hemoglobin variant was detected by electrospray ionization mass spectrometry. Hb Zurich-Hottingen is characterized by an Asn --> Ser replacement in the alpha-chain at position 9 as confirmed by DNA analysis. This hemoglobin variant is silent in isoelectric focusing, reversed-phase chromatography, and cation-exchange chromatography. The mutant alpha-chain was detectable only with electrospray mass spectrometry by its mass shift of -27 Da. The carrier was found to be heterozygous for the new hemoglobin variant. These results illustrate the power of ESI mass spectrometry for hemoglobin analysis.